Lumber sorters are used in sawmills to sort lumber as it is produced from timber stock which is introduced into the sawmill to be cut into board lengths. During the course of processing of the timber stock into board lumber, various lengths of board lumber are produced from the timber stock of varying widths, thicknesses and lengths. To facilitate processing of like dimensioned board lumber, one or more of the dimensions of width, thickness or length of the board lumber are used for sorting. For example, certain dimensioned board lumber can be selected for processing into 8 foot 2×4's and this lumber can be sorted into a common bin or group of bins. The sorting of board lumber after initial cutting is generally carried out on an automated basis by a bin lumber sorting system. A bin lumber sorting system has a plurality of open topped bins to receive board lumber. The lumber to be sorted is provided to the bin lumber sorting system on a feed conveyor where it is transferred to a sorting conveyor. The sorting conveyor delivers the lumber to a target open topped bin to carry out the sorting process. In the bin lumber sorting system, it is the sorting conveyor that moves the lumber across a plurality of upwardly open bins to the open topped bin that is targeted to receive selected boards matching the dimensional parameters assigned to that bin. A typical bin lumber sorting system may include anywhere from tens to several hundreds of bins to receive the board lumber to be sorted.
There are existing board and lumber transport devices for transporting lumber to sorting bins that rely on a sorting conveyor system for example, a J-hook sorter, a push lug sorter, or a drag chain sorter.
FIG. 1 is a side elevation view of a portion of a lumber sorter known, for example, from Canadian patent application number 2,383,558 published on 2003-10-26, showing a portion of a feed conveyor 10 and a sort conveyor 20. Feed conveyor 10 delivers pieces of board lumber 12 along an upper surface 14, which may be, for example, a rail or a chain. Pieces of board lumber 12 are ambulated along upper surface 14 at predetermined intervals determined by the spacing of lugs 16 on upper surface 14. Upper surface 14 advances dependent on rotation of pulley 18 in a clockwise direction, which results in transport of pieces of board lumber 12 along upper surface 14 toward pulley 18, which may be a sprocket. Sort conveyor 20 obtains pieces of board lumber 12 from feed conveyor 10. Sort conveyor 20 has a pulley 22, which may be a sprocket, which rotates in a counter-clockwise direction to move a belt 34 (which may be a flexible belt or a chain, as desired) around the periphery of pulley 22 and in the direction of arrow 24. Hooks 26 are pivotally connected to belt 34 and are conveyed along with belt 34. As successive hooks 26 of sort conveyor 20 move laterally in approach to pulley 22, hooks 26 are supported in an inverted position by resting on support guide 28. Support guide 28 ends near pulley 22 permitting each hook 26 passing in the region between the end of support guide 28 and pulley 22 to rotate about pivot 30 to move hook shoulder 31 toward stop 32 of pulley 22. As the belt 34 conveys each hook 26 around the periphery of pulley 22, stop 32 restrains the rotation of each hook 26 to orient hook an opening 43 of each hook towards feed conveyor 10 in preparation to transfer pieces of board lumber 12 from supply conveyor 10 to the sort conveyor 20.
The transfer of pieces of board lumber 12 from feed conveyor 10 to sorting conveyor 20 occurs in the transfer region where the two conveyors overlap. To transfer pieces of board lumber 12, the distal end 36 of hook 26 is positioned below the upper surface 14 of the feed conveyor 10. When the hook 26 has reached a transfer point, hook 26 rotates about its pivot 30 to permit a support arm of hook 26 to descend below and pass beneath a piece of board lumber 12 on feed conveyor 10 in the direction of arrow 38. In this manner, lugs 16 and distal ends 36 of each of the hooks 26 define a transfer area for the pieces of board lumber 12 to be transferred from the feed conveyor 10 to the sorting conveyor 20.
Support guide 28 supports hooks 26 and belt 34 while they travel along the top run of sort conveyor 20. Support guide 29 supports hooks 26 and belt 34 as they travel along the bottom run of sort conveyor 20. While a hook 26 is travelling along support guide 29, it is free to rotate about pivot 30 and may rotate an undesirable amount. Undesirable excess rotation may cause improper functioning of the lumber sorter.
An apparatus for limiting the rotation of the hook is desired.